In the offshore industry, the exploration and production of gas and petroleum is conducted through tubulars of various diameters that are cemented inside each other and extend to a distance below the sea floor, where the production zone is located. When the well is abandoned, the owner of the offshore rig is required to remove the casing at the depth of 20 feet below the mud line. After the casing is cut, the rig owner must cement the plug on the abandoned well to protect the marine life in the surrounding area.
To perform the cutting operation below the mud line, a cutting tool is lowered into the innermost casing, which usually has a relatively small diameter, and severs the tubulars. When the first inside casing is removed, another cutter with greater cutting diameter is lowered inside the pipe and the next diameter conduit is cut in a similar manner. This procedure continues until the multiple tubulars are cut at the required depth.
Conventionally, the industry uses a three-blade cutting tool, which will first cut the 7-⅝″ pipe, then another cutting tool that will cut 10-¾″ diameter pipe, etc. If the inner casing collapses, the job becomes even more complicated and the casing needs to be drilled out or severed by an explosive to remove the smallest diameter casing. The conventional three-blade tool has cutter blades equidistantly spaced about the circumference of the tool body. The distance between the cutter blades in a conventional tool suitable for fitting into the smallest diameter pipe is relatively small. Since the inner diameter of the tubular has very small tolerances, the cutter blades have to be sufficiently small, as well, to allow lowering into the small diameter innermost tubular. The cutter blades of a conventional tool are often damaged, requiring pulling the tool to the surface and starting the process again. The painstaking process takes several days over the use of conventional tools.
If the inner casing collapsed, it may become completely impossible to mill out the necessary portions of the tubulars. In that case, the casing must be cut from the outside, first excavating the mud around the casing to the required depth and then applying the cutting tool to do the job. Such procedure is also expensive and takes several days.
My casing cutter tool disclosed in U.S. Pat. No. 7,063,155 solves the above-described problems by providing a casing cutter that has a pair of cutter blades pivotally mounted on a support body. The blades are pivotally mounted for gradual movement outside of the support body when downward force is applied to proximate ends of the cutter blades. The support body is rotated inside the innermost of the multiple tubulars, while the cutter blades sever the tubulars of progressively increasing diameter. The cutting blades have a main top surface and a distal end wall. The cutting elements are located on the main top surface and on the distal end wall. When the cutter blades are gradually pivotally moved from an idle position recessed in the hollow body to a position substantially perpendicular to the vertical axis of the body the top surface mills out a window in the casing, severing the casing to allow a subsequent plugging operation to take place.
While the tool of the '155 patent works satisfactory, it was observed during the tests that the cutter blades or the pivot pins carrying the blades sometimes become damaged, which requires that the tool be repaired with new blades or new pivot pins. Naturally, the blade or pin replacement takes time, which slows the casing cutting process.
The present invention contemplates elimination of the drawbacks associated with the prior art and provision of a casing cutter that can be used for cutting multiple tubulars in an efficient manner that allows to save time and expense of the operation. The cutting tool is reversible, allowing the tool to be turned 180 degrees, with new cutting blades to continue the casing milling operation.